There is a continuing need for improved methods and apparatuses for compressing/encoding data and decompressing/decoding data, and in particular image and video data. Improvements in coding efficiency allow for more information to be processed, transmitted and/or stored more easily by computers and other like devices. With the increasing popularity of the Internet and other like computer networks, and wireless communication systems, there is a desire to provide highly efficient coding techniques to make full use of available resources.
Rate Distortion Optimization (RDO) techniques are quite popular in video and image encoding/decoding systems since they can considerably improve encoding efficiency compared to more conventional encoding methods.
The motivation for increased coding efficiency in video coding continues and has recently led to the adoption by a standard body known as the Joint Video Team (JVT), for example, of more refined and complicated models and modes describing motion information for a given macroblock into the draft international standard known as H.264/AVC. Here, for example, it has been shown that Direct Mode, which is a mode for prediction of a region of a picture for which motion parameters for use in the prediction process are predicted in some defined way based in part on the values of data encoded for the representation of one or more of the pictures used as references, can considerably improve coding efficiency of B pictures within the draft H.264/AVC standard, by exploiting the statistical dependence that may exist between pictures.
In the draft H.264/AVC standard as it existed prior to July of 2002, however, the only statistical dependence of motion vector values that was exploited was temporal dependence which, unfortunately, implies that timestamp information for each picture must be available for use in both the encoding and decoding logic for optimal effectiveness. Furthermore, the performance of this mode tends to deteriorate as the temporal distance between video pictures increases, since temporal statistical dependence across pictures also decreases. Problems become even greater when multiple picture referencing is enabled, as is the case of H.264/AVC codecs.
Consequently, there is continuing need for further improved methods and apparatuses that can support the latest models and modes and also possibly introduce new models and modes to take advantage of improved coding techniques.